title: Determination of Young's modulus for nanofibrillated cellulose multilayer thin films using buckling mechanics.
abstract: The Young's modulus of multilayer films containing nanofibrillated cellulose (NFC) and polyethyleneimine (PEI) was determined using the strain-induced elastic buckling instability for mechanical measurements (SIEBIMM) technique. (1) Multilayer films were built up on polydimethylsiloxane substrates using electrostatic layer-by-layer assembly. At 50% relative humidity, SIEBIMM gave a constant Young's modulus of 1.5 ± 0.2 GPa for 35-75 nm thick films. Conversely, in vacuum, the Young's modulus was 10 times larger, at 17.2 ± 1.2 GPa. A slight decrease in buckling wavelength with increasing strain was observed by scanning electron microscopy with in situ compression, and above 10% strain, extensive cracking parallel to the compressive direction occurred. We conclude that whereas PEI acts as a "glue" to hold multiple layers of NFC together, it prevents full development of hydrogen bonding and specific fibril-fibril interactions, and at high humidity, its hygroscopic nature decreases the elastic modulus when compared with pure NFC films.
authors.affiliation: Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, The Royal Institute of Technology, SE-100 44 Stockholm, Sweden. cranston@kth.se
authors.forename: Emily D
authors.initials: ED
authors.lastname: Cranston
authors.forename: Mohamed
authors.initials: M
authors.lastname: Eita
authors.forename: Erik
authors.initials: E
authors.lastname: Johansson
authors.forename: Julia
authors.initials: J
authors.lastname: Netrval
authors.forename: Michaela
authors.initials: M
authors.lastname: Salajková
authors.forename: Hans
authors.initials: H
authors.lastname: Arwin
authors.forename: Lars
authors.initials: L
authors.lastname: Wågberg
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures
chemical_list: D002482:Cellulose